1. Field of the Invention
The invention relates to operation of main and branch networks of pressure and free-flow metal pipeline, and more particularly, it deals with an apparatus for cleaning the inner surface of pipelines from deposits and for forming a protective coating.
Description of the Prior Art
Known in the art are various methods and apparatuses for cleaning the inner surface of pipelines from deposits. However, while solving the problem of cleaning, they cannot bring a solution to the problem of reliable protection of the pipeline surface against corrosion during cleaning. Thus known in the art is a method for cleaning simultaneously with the protection of the pipeline surface against corrosion, comprising forming a layer of coating on the surface of a pipeline during cleaning by removing deposits and by compacting the remaining layer, all operations being conducted mechanically (cf. USSR Inventor's Certificate No. 1018729, Cl. B 08 B 17/00, publ. May 23, 1983). However the coating thus formed cannot hamper the development of pit corrosion which is detrimental to the pipeline as foci of corrosion remain intact in the compacted layer.
The most widely used the world over is a hydromechanical method for cleaning a pipeline from deposits which comprises causing a self-contained pipe cleaning unit to move along a pipeline under the action of a gauge water pressure, the unit comprising blade-shaped flexible members mounted in a checkerboard fashion, a part of water flowing through the unit to remove deposits separated from the walls by the cutting members of the apparatus (cf. USSR Inventor's Certificate No. 856599, Cl. B 08 B 9/04, publ. Aug. 23, 1981; USSR Inventor's Certificate No. 716647, Cl. B 08 B 9/04, publ. Feb. 25, 1980).
In using this method, the pipeline is cleaned to expose metal, but quality of the surface treatment is inadequate to apply an antitrust coating thereto since a part of corrosion deposits remains in shells and pores of the pipeline surface so as to result in the development of pit corrosion in the pipeline walls later on. In addition, damages to the pipeline surface induced by the apparatus result in that the surface cleaned to expose metal is corroded immediately after the cleaning.
Known in the art is an apparatus for a hydrodynamic cleaning. The apparatus comprises a cleaning tool having a hub carrying spring blades secured thereto to engage the pipeline surface, the blades being arranged in rows and spaced with respect to one another so as to define apertures along their periphery. (cf. USSR Inventor's Certificate No. 995910, Cl. B 08 B 9/04, publ. Feb. 25, 1983). Owing to a structural imperfection of the cleaning tool, a part of energy of the flow of fluid passing through the apertures between the blades is spent to overcome resistances offered by the blades of the apparatus so that fluid jets lack necessary power to wash deposits off the pipeline walls, and a durable protective coating cannot be formed in the pipeline.